1. Field of the Invention
The present invention relates to a polishing composition, a process for reducing surface defects of a substrate with the polishing composition, and a process for manufacturing a substrate with the polishing composition.
2. Discussion of the Related Art
Recent memory hard disk drives have been demanded to have high areal density and small size. In order to increase the areal density, it has been strongly urged to lower flying height of a magnetic head and to reduce the unit area of recording. Along with this trend, the surface quality required after polishing has become severely assessed every year even in a process for manufacturing a magnetic disk substrate. In order to meet the requirement of lower flying height of the magnetic head, the improvement in surface smoothness and the reduction in surface defects have been desired.
In order to meet such requirements, there have been proposed polishing compositions with improved surface smoothness such as surface roughness Ra and Rmax, scratches, pits and projections (see Japanese Patent Laid-Open No. Hei 11-167715 and Japanese Patent Laid-Open No. Hei 11-246849 (corresponding to U.S. Pat. No. 6,149,696)). However, as a consequence of improved surface smoothness, there have been newly found surface defects such as pits and projections which have not been detected so far. Therefore, the reduction of the generation of such surface defects is a problem to be solved.